If you are going to 2012, think about FileTable. In some ways the development is easier than Filestream.
The filters for blobs are based on the iFilter standard. You can purchase third party filters for some types, or that work better. The Office filters work pretty well, but if you are Office 2010 or later, you'll need to download and install them separately. The native iFilters for FTS are 2007 based.
For file sizes, in general, if you are 256kb or smaller, use varbinary and stick them in there. If your files are 1MB or larger, go Filestream/Filetable. In between, test, but if you don't have lots of updates (mostly inserts), I'd just do Filestream/Filetable and not worry about it.
I wouldn't look at Semantic Search in 2012. It is a neat idea, but it only supports uni-grams (single terms) and isn't terribly useful, IMHO. FTS searches work better. If they get to n-grams in 20xx, then I'd revisit this. With that in mind, separate and contain your search logic so you can replace it if things improve or you want to change things. The NEAR and proximity searches are improved in 2012. You also get property searches, so the "tags" and metadata you see in the file properties or explorer windows can be searched in 2012. That's pretty cool stuff if your sources use it.
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